Dual Channel DDR 400

weks

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This is a n00b question but...
If I buy a motherboard that supports DC DDR400 does the processor got to support DC DDR400 too?
As faar as I was concerned until recently the only thing that had to support DC DDR400 was the motherboard, not the processor...
And if the processor got to support it too does the AMD Athlon XP 2700+ Support Dual Channel DDR400?
If you understand what I am saying?

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pIII_Man

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well, you are right, theoretically you could make a chipset for a K6 that would give it dual channel support...however just because the chipset supports it does not mean the cpu can take advantage of it...

for example the fsb bandwith of an athlon xp cpu with 400 (200mhz physical) fsb is 3200mb/s

the max bandwith of standard ddr400 in single channel is 3200mb/s

max bandiwth of ddr400 dual channel is 6400mb/s

max bandwith of 800mhz (200mhz physical) fsb p4 is 6400mb/s

as you may see...an athlon xp cpu wont get much of a performance increase from dual channel because it cannot take advantage of the extra bandwith, but this by no means states that athlon xps are not compatable with dual channel.

If it isn't a P6 then it isn't a processor
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Coyote

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Umm... where to start. Lots of stuff (prolly unintentionally) rolled into this question.

OK, first you're talking AMD here. Intel is different (AMD's do not take full advantage of the DC technology like Pentium's do. But I assume you are going the AMD route)


"If I buy a motherboard that supports DC DDR400 does the processor got to support DC DDR400 too?"

No, because it's mobo for AMD (anyway, if the mobo required the cpu to support it, that w/b a pentium and the mobo would say it supported 800mhz)

"As faar as I was concerned until recently the only thing that had to support DC DDR400 was the motherboard, not the processor..."

Correct for AMD cpu's

"And if the processor got to support it too does the AMD Athlon XP 2700+ Support Dual Channel DDR400???
If you understand what I am saying?"

Basically now irrelevany question based on answers above. However, I think the XP 2700 has a FSB of 133 (or 2 x 133 = 266 due to double data rate of DDR ram). So, to get that chip up to DDR400 you need to OC the FSB from 133 > 200 (200 x 2 for DDR =400). The XP 3200+ is the only one for that mobo which natively runs at FSB of 200 (2 x 200 = DDR400)IIRC

The Barton 2500+ with a FSB of 166 (DDR 333) is commonly OC'd to the XP3200+ by raising it's FSB to 22 (400DDR)


To answer your question in simplest terms, that cpu will work on the board, but not at the top speed the board can handle. You will be able to use DC with that cpu. You will be able to upgrade the cpu with that board (unless you can OC the XP2700+ to FSB of 200).

You've got the issues of DC, and FSB, and DDR all rolled into this one question.

Hope this is helpful



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pIII_Man

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damn skiped over that....the 2700 is a 333 (166mhz physical) fsb chip..yeilding 2666.66 MB/s max bandwith...

If it isn't a P6 then it isn't a processor
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Crashman

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P4's use a Quad Data Rate CPU bus, dual channel allows you to multiply the bandwidth of Double Data Rate memory by 2, making the memory bus and CPU bus bandwidth equal.

Athlon XP's and earlier use a Double Data Rate CPU bus, so they don't need the extra bandwidth of dual channel

PIII base processors and earlier technology uses a single data rate CPU bus, it doesn't even make use of DDR, let alone dual channel DDR.

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weks

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Right... Um...
So you are saying:
1. That I don't need the mobo to support the DC, because it's usless for AMD?
or
2. Buy a Pentium (whit a good mobo)
or
3. *Insert something here*

And if I buy a XP 2700+ what motherboard shuld i get (I got to be fast)

Thx for all your help.

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addiarmadar

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Dual Channel is strictly between the RAM and the mobo. All CPUs can work with the ram in dual channel mode. Just get a CPU that does at least 166 clock in which you can OC it to 200 clock. Some mobile chips with 133 clock can easily do 200 but it gets wired there.

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